Head Bobbing

I watched the seagulls at the wharf today. (There was nothing else to watch) and noticed them performing an odd behaviour. The majority of a group of about 10 birds were standing  rapidly bobbing their heads in and out of the water. One or two were bathing normally as birds do, but this was just a head action and it was very fast. After each sequence, the bird would rear up, stretch the wings, then back down to start the bobbing again.

This bird was at the stretch the wings up stage and I barely had time to take a shot before it was back to the head bobbing business. If you look carefully you will see how wet its head is - and it is only the head that gets so wet.